title: A review of recent neurochemical data on inert gas narcosis.
abstract: Nitrogen narcosis occurs in humans at around 0.4 MPa (4 ATA). Hydrogen narcosis occurs between 2.6 and 3.0 MPa. In rats, nitrogen disturbances occur from 1 MPa and a loss of righting reflex around 4 MPa. Neurochemical studies in striatum of rats with nitrogen at 3 MPa (75% of anesthesia threshold) with differential pulse voltammetry have demonstrated a decrease in dopamine (DA) release by neurons originated from the substantia nigra pars compacta (SNc). Such a decrease is found also with compressed argon, which is more narcotic than nitrogen and with the anesthetic gas nitrous oxide. Inversely, compressed helium with its very low narcotic potency induces DA increase. Microdialysis studies in the striatum have indicated that nitrogen also induces a decrease of glutamate concentration. Nitrogen pressure did not modify NMDA glutamate receptor activities in SNc or striatum but enhanced GABAA receptors activities in SNc. Repetitive exposures to nitrogen narcosis suppressed the DA decrease and induced an increase. This fact and the lack of improvement of motor disturbances did not support the hypothesis of a physiological adaptation. The desensitization of the GABAA receptors on DA cells during recurrent exposures and the parallel long-lasting decrease of glutamate coupled to the increase in NMDA receptor sensitivity suggest a nitrogen neurotoxicity or addiction induced by recurrent exposures. The differential changes produced by inert gases indifferent neurotransmitter receptors would support the binding protein theory.
authors.affiliation: Université de la Méditerranée et IMNSSA UMR-MD2, Physiologie et Physiopathologie en Condition d'Oxygénation Extrême, Faculté de Médecine Nord, Institut de Neuroscience Jean Roche, 13015 Marseille, France. jean-claude.rostain@univmed.fr
authors.forename: J C
authors.initials: JC
authors.lastname: Rostain
authors.forename: C
authors.initials: C
authors.lastname: Lavoute
authors.forename: J J
authors.initials: JJ
authors.lastname: Risso
authors.forename: N
authors.initials: N
authors.lastname: Vallée
authors.forename: M
authors.initials: M
authors.lastname: Weiss
mesh_terms: D000222:Adaptation, Physiological; D000777:Anesthetics / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D001274:Atmospheric Pressure; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D003461:Crystallography / Q000379:methods; D004298:Dopamine / Q000032:analysis / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D006371:Helium / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D006859:Hydrogen / Q000378:metabolism / Q000494:pharmacology; D007222:Inert Gas Narcosis / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D008051:Lipid Bilayers / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D011963:Receptors, GABA-A / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism; D013378:Substantia Nigra / Q000187:drug effects / Q000378:metabolism*; D014503:Urate Oxidase / Q000378:metabolism
chemical_list: D000777:Anesthetics; D017304:Annexin A5; D008051:Lipid Bilayers; D008565:Membrane Proteins; D011963:Receptors, GABA-A; D016194:Receptors, N-Methyl-D-Aspartate; D006371:Helium; D018698:Glutamic Acid; D016202:N-Methylaspartate; D006859:Hydrogen; D014503:Urate Oxidase; D009584:Nitrogen; D004298:Dopamine